Αλυσίδα μοτοσικλέτας 420 Standard | Βήμα 12,700 mm, 15,6 kN

The 420 motorcycle chain is a roller drive chain with a 12.700 mm pitch and 6.35 mm inner width — the narrowest and lightest of the commonly-used 1/2-inch pitch family. It occupies the lightest end of the standard motorcycle chain spectrum, designed for engines where output is moderate and where minimising rotating mass and chain weight genuinely contributes to overall machine performance. At 0.57 kg/m and 15.6 kN tensile strength, the 420 handles the torque range of 50cc to approximately 125cc four-stroke engines with comfortable headroom.

The 420 pitch is standard fitment on most 50cc mopeds, entry-level 125cc motorcycles, many off-road dirt bikes in the 50–110cc class, and a wide variety of ATVs and smaller recreational off-road vehicles. Its light weight is genuinely beneficial on these machines — a 420 chain is measurably lighter than a 428 or 520 unit, and on a 70kg machine with a 4kW engine, that matters more than on a 200kg touring bike with a 60kW engine.

Αριθμός αλυσίδας	Βήμα (mm)	Τύπος Μπους	Πλάτος (mm)	Διάμετρος καρφίτσας (mm)	Μήκος καρφίτσας (mm)	Διάμετρος κυλίνδρου (mm)	Πλάκα T Εσωτερική (mm)	Πλάκα T Εξωτερική (mm)	Αντοχή σε εφελκυσμό (kN)	Βάρος (kg/m)
420	12.700	Κατσαρωμένο	6.35	3.96	14.70	7.77	1.50	1.50	15.6	0.57

All three pitches belong to the 12.70 mm (1/2 inch) pitch family but carry different inner widths and consequently different roller contact areas. The pitch number encodes both pitch (first two digits: "42" = 4/8 inch × 10 = 12.7 mm; "52" = 5/8 inch × 10 = 15.875 mm) and width class (last two digits). For bikes currently running a 420, attempting to fit a 428 or 520 requires sprocket replacement — the sprockets are not interchangeable between inner width families. Confirm your existing chain's stamped number before ordering any replacement.

Προσδιορισμός	420 (This Chain)	428	520
Βήμα (mm)	12.700	12.700	15.875
Inner width (mm)	6.35	7.85	6.35
Roller diameter (mm)	7.77	8.51	10.16
Tensile strength (kN)	15.6	17.8	26.5
Βάρος (kg/m)	0.57	0.71	0.91
Typical engine displacement	50–125cc	125–250cc	250–600cc
Common applications	Mopeds, mini dirt bikes, small ATVs	125–250cc street, off-road	Mid-range sport and naked bikes
Sprocket interchangeability	420 sprockets only	428 sprockets only	520 sprockets only

The 420's narrower width versus the 428 (6.35 vs 7.85 mm inner) is the most significant physical difference between the two same-pitch options. Both use 12.70 mm pitch — and that's the only dimension that matters for sprocket mesh — but the 420's narrower roller means it will not seat correctly in a 428 sprocket's tooth spacing. Always check whether your sprockets are stamped 420 or 428 before ordering, especially on bikes where previous owners may have upgraded the αλυσίδα μοτοσικλέτας without replacing the sprockets.

The 420 pitch occupies a clear niche. Understanding both what it does well and where its limits are helps ensure you're choosing the right specification for your actual riding needs, not simply defaulting to a "bigger is better" upgrade that adds weight without benefit.

A 420 standard chain should be lubricated every 400–600 km under normal paved-road conditions, or more frequently if you ride in wet or dusty environments. The curled-bushing construction means the internal joint relies entirely on externally applied lubricant — once that film dries out or is displaced by road grime, pin-bushing wear accelerates rapidly. On scooters covering short daily distances, time can also be a practical trigger: if three weeks have passed since the last lubrication regardless of mileage, lube the chain before the next ride.

Climate note: In humid Korean summer conditions or during the monsoon period, lubricate after any ride longer than 300 km or after any wet ride. Road spray strips lubricant from non-sealed chains more rapidly than dry conditions suggest.

The front and rear sprockets define the final drive ratio — the ratio of rear sprocket tooth count to front sprocket tooth count. On a 420-equipped machine with 14 front teeth and 42 rear teeth, the ratio is 3.0:1, meaning the rear wheel turns once for every three crankshaft rotations at the engine's output shaft (after the gearbox). Increasing the rear sprocket tooth count (or reducing front) raises the ratio, giving more acceleration at the cost of top speed. Reducing rear teeth (or adding front) lowers the ratio, raising top speed while reducing low-end pull.

For the standard 420 specification, sprocket material is typically steel — providing the best durability match for a chain expected to cover 8,000–15,000 km before replacement. Aluminium sprockets on a 420 machine are uncommon because the weight saving relative to the machine's overall mass is negligible, and steel outlasts aluminium by a significant factor at this chain pitch and power level.

When replacing the chain, inspect both sprockets. Tooth tips that appear pointed or thinned, or leading tooth faces with a hook-shaped profile, mean the sprockets should be replaced simultaneously. Fitting a new 420 chain on worn sprockets will accelerate the new chain's elongation rate considerably — the worn sprocket shifts load onto the chain's side plates rather than the rollers, which is not how 420 chains are designed to carry load.

Can I use a 428 chain on a bike that currently runs a 420?
Not without replacing both sprockets. The 420 and 428 share the same 12.70 mm pitch, so the chain links engage at the same spacing — but the inner width difference (6.35 mm vs 7.85 mm) means the roller will not seat correctly in 420 sprocket tooth gaps if a 428 chain is fitted. The chain will either bind or ride incorrectly on the teeth, causing rapid wear and safety risk. Only fit a 428 chain if you also replace both sprockets with 428-specification parts.

What is the difference between a 420 and 415 chain?
The 415 has the same 12.70 mm pitch but an even narrower inner width of approximately 4.76 mm (versus 6.35 mm for the 420). The 415 is used on very small-displacement machines — 50cc racing and some mini-bikes — where minimum chain weight is the priority. The 420 is the more common choice because the wider roller provides a larger contact area on the sprocket tooth, reducing tooth wear rate at equivalent loads.

How do I measure 420 chain stretch to decide when to replace?
Measure 20 consecutive links (pin centre to pin centre across 20 links) under slight tension applied to the chain. The nominal 20-link distance is 20 × 12.70 = 254.0 mm. Replace the chain when the measured length exceeds 261.6 mm (3% elongation). Also pull the chain away from the rear sprocket at the centre of the chain run — if you can expose more than half a tooth root, the chain is worn beyond adjustment range.

Is the 420 available in a sealed O-ring version?
The 4205-O (O-ring sealed, 12.70 mm pitch, 6.35 mm inner width) is the sealed equivalent. It uses the same pitch and sprocket compatibility as the 420 but with solid bushing construction and O-ring seals at each joint, extending lubrication intervals to 600–1,000 km and delivering considerably longer service life in wet or off-road conditions. Contact us to confirm availability and specification details.

How many links does a 420 chain typically have?
Link count varies by machine — it depends on the rear wheel travel distance (distance from front to rear sprocket) and the sprocket tooth counts. Common 420 link counts for 50–125cc machines range from 96 to 120 links, but confirm the exact count from your owner's manual or by counting the links on the removed chain. Ordering the wrong link count requires adding or removing links at the master link, which is possible but adds a step to the installation.

Park Jae-woo, Scooter Fleet Manager, Seoul (February 2025)
"We run 15 delivery scooters on 420 chains with a monthly replacement rotation. The quality from Korea Ever-Power is consistent batch to batch — same stretch characteristics, same installation fit. Our maintenance cost per bike has been stable since switching. No quality-related chain failures in eight months."

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Kim Hyun-ki, Pit Bike Racer, Gyeonggi-do (January 2025)
"Running a 420 on a 110cc pit bike at club events. The chain is noticeably lighter than the 428 I used to run — on a 65kg machine the weight difference in rotating components is actually relevant. Korea Ever-Power's 420 holds tension consistently across a weekend of track use. Lubing between sessions keeps it in good shape."

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Lee Young-hoon, Student Commuter, Daejeon (December 2024)
"Fitted a 420 on my 50cc moped myself — no experience beforehand, but the installation is straightforward. The chain came with a clip link and installed without issues. Running it every day for four months, lubing every 400 km. No tension problems and no rust, even through the rainy stretch in December."

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Choi Tae-jin, Motorcycle Parts Retailer, Busan (November 2024)
"The 420 is one of our top-moving SKUs for the small scooter and moped market. Korea Ever-Power's supply is reliable and the quality is consistently acceptable to our customers. We've had very few returns on this chain — the occasional dimensional query is always resolved quickly by their team."